MINNEAPOLIS (WCCO) — The National Transportation Safety Board says weather was a major factor in September’s medical helicopter crash in Alexandria, which seriously injured three people.

Officials say a North Memorial Medical Center helicopter was flying from Brainerd Lakes Regional Airport to Douglas County Hospital just after 2 a.m. on Sept. 17. There was one pilot and two crew members aboard.

The NTSB says the helicopter lost contact with air traffic control halfway on its journey. Clouds started forming beneath the aircraft, creating a challenge for landing.

The helicopter missed the approach while beginning to land in Alexandria and banked left to right, eventually colliding with tall trees before crashing on Chandler Field Airport near the hospital.

The crew members were hospitalized in critical condition. Two have been released since the crash.